Car-spring



i UNITED STATESN PATENT OFFICE.

JOHN B. N. BERRY, OF BALTIMORE, MARYLAND.

CAR-SPRING.

SPECIFICATION forming part of Letters Patent No. 255,835, dated April 4, 1882.

Application tiled December 15, 1881. (No model.)

To all whom it may concern:

Be it known that I, JOHN B. N. BERRY, of Baltimore city, State of Maryland, have invented'certain new and useful Improvements in Gar-Springs; and I hereby declare the saine to be fully, clearly, and exactly described as follows, reference heilig had to the accompanying drawings, in which- Figure l is a side elevation of the spring. Fig. 2 is a top plan of the same; and Figs. 3` and4are plans of the blanks which constitute, when coiled, the members of the spring'.

My invention relates to car-springs of the spiral volute class; and it has for its object to` produce a spring in which the tension is substantially equalzed throughout its length, and in which the metal is not materially strained in 'the bending.

It is an observed fact, and due to obvious causes, that a spiral springwin which the bar is uniform in cross-section throughout its length does not settle uniformly when subjected to pressure, and it has been sought to render spiral springs uniform in their action, either by tapering the blank edgewise from the fulcrum-point to the ends or by tapering it flatwise, or by a combination of both tapers. These methods are all objectionablethe last tivo by reason of the practical impossibility of rolling a blank with a taper, (and a flatwise taper is only attainable by forging,) and the former by reason of the fact that the two sides of the coil are subjected to a strain in ceiling, which detracts greatly from the strength of the spring. I remedy the evil by constructing a spring as follows: Two or more blanks are cut from material of uniform thickness in the shape shown in Figs. 3 and 4-that is to say,

the blanks have an edgewise taper-and these blanks are then rolled u p together to form the cone-spiral. The blanks may be of the same or dierent lengths and of the same or different thickness.

In the drawings, A and B are the blanks, having tapers from their fulcrum-points a and b; and Gis aninclosingcylindre-spiral formed from a tapering barand coiled about the spring A B, as shown. It serves to re-enforce the spring and ts iu the upper and lower bearings of the conventional spring-seats, and is adapted to sustain an exterior cover of textile fabric, leather, or rubber, which may be used to protect the spring from access of grit, 86o.

1t is clear that the strain of expansion on the exterior and compression on the interior surfaces of a bar or plate, when bent in a curve, diminishes, ceter'spai'ibus, with the thickness of the material, and in a plate of infinite thinness would amount to nothing. The theoretically perfect spring would therefore consist of au infinite number of infinitely thin plates, each having the proper edge taper. Multiplying the plates is found in practice to be of no material benefit, as the strain in a thin plate may be removed, to al1 intents and purposes, by careful annealing, and a spring consisting of from two to four plates is found to answer every requisite, especially when for heavy work it is re-enforced by the exterior coil, C.

The coils of the spring close down uniformly, in consequence of which, and of the further fact that the metal of the separate coils is not strained periplierally, the spring is iound to be most durable and satisfactory.

By making the leaves of unequal length the coil B projects at the top of the spring, as shown, and thereby the e'eet of a iiatwise taper is secured, the springB operating alone until the upper bearing descends upon the lower spring, A. The leaves Aand B are uhattached to each other, whereby the renewal of either, when' broken or injured, is facilitated. Were they riveted or otherwise connected together this could not be done.

Having th us described my invention, what I claim as new, and desire to secure by Letters Patent, is

l. A car-spring consisting of t'wo or more volute spiral members, each of uniform thickness throughoutits length and having an edgewise taper, the said vmembers being of different lengths, as and for the purpose set forth.

2. A car-spring consisting of two or more volute spiral members, each of uniform thickness throughout its length and having an edgewise taper and an inclosing cylindre-spiral adapted to sustain a covering, as and for the purpose set forth.

3. A car-spring consisting of two or more volute spiral members, each of uniform thick-` ness and having an edge taper, the said members being concentrically coiled and unconnected with each other, as set forth.

JOHN B. N. BERRY.

Witnesses R. D. WILLIAMS, ED. RAINE.

IOO 

